This invention relates to novel fluorinated aromatic polyethers which are useful as dielectric materials in microelectronic articles.
Polymer films and coatings are often used in the electronic industry as insulating materials and passivation layers, especially in integrated circuit devices such as multichip modules. Polymers having a low dielectric constant .epsilon. are preferred, because components insulated with them can be designed with higher circuit densities and can operate at higher speeds and with less signal broadening. The effect of .epsilon. on the performance of multilayer integrated circuit articles is discussed in "Microelectronics Packaging Handbook," Tummala et al. (eds.), pp. 687-692 (van Nostrand Reinhold); Watari et al., U.S. Pat. No. 4,744,007 (1988); and Budde et al., U.S. Pat. No. 4,732,843 (1988).
Polyimide is an insulator of choice for many electronic applications, because of its superior mechanical and thermal properties and its fabricability into thin films and coatings. However, polyimide has a relatively high .epsilon., a limitation accentuated by polyimide's tendency to absorb water (up to 3-4%) in humid environments. Water absorption causes .epsilon. to rise, compromising performance. Once commercially available polyimide has an .epsilon. of about 3.2 at 0% relative humidity (% RH), which rises to about 3.8 at 60% RH. As noted by Denton et al. in J. Electronic Mater, 14(2), 119 (1985), polyimide moisture absorption can also adversely affect performance through increased insulator conductivity, loss of adhesion, or corrosion. Further, some polyimides are susceptible to hydrolysis and/or attack by solvents (often manifested by crazing or cracking upon exposure to a solvent).
It has been proposed, in Mercer, U.S. Pat. No. 4,835,197 (1989), to improve the solvent resistance of polyimide by curing with an acetylene, maleimide, or vinyl terminated curing agent. However, a polyimide so cured would still have the relatively high dielectric constant of polyimides and their tendency to absorb moisture.
Mercer, in copending commonly assigned application Ser. No. 07/447,771, filed Dec. 8, 1989, proposes using fluorinated polymers having a binaphthyl moiety as dielectric materials.
Polyquinoxalines, polyquinozalones, polybenzoxazoles, and copolymers thereof with polyimides have also been proposed as polymers for microelectronic applications by Labadie et al., in SAMPE J. vol. 25, pp. 18-22 (November/December 1989).
Kellman et al., ACS Symp. Ser. 326, Phase Transfer Catalysis, p. 128 (1987) discloses the preparation of polyethers from diphenols and hexafluorobenzene and decafluorobiphenyl, although no particular utility is disclosed for the polymers so prepared. Similar disclosures are made in Kellman et al., Polym. Prepr. 22(2), 383 (1981) and Gerbi et al., J. Polym. Sci. Polym. Letters Ed. 23, 551 (1985).
This invention provides a fluorinated poly(arylene ether) which is especially suitable as a dielectric material in electronic articles. The polymers of this invention have low dielectric constants which are little affected by increases in the ambient humidity, can be made solvent resistant, and exhibit excellent adhesion to itself and other adherends.